1. Field of the Invention
The present invention relates to a travel gear of a crawler work vehicle.
2. Description of the Related Art
A conventional travel gear of a crawler work vehicle can travel, for example as shown in FIG. 6, generally by providing a pair of right and left track frames 2 and 2 in the lower part of the body in the longitudinal direction of the vehicle, rotating a crawler 6 rotatably wound around the track frames 2 via a sprocket 4, and rolling a plurality of track wheels 11 rotatably attached to the lower part of the track frame 2 on the inner face (hereinbelow, called a wheel tread) of the crawler 6.
FIG. 7 shows a first prior art of such a travel gear, and is a side view of a travel gear having a fixed track wheel disclosed in Japanese Patent Publication No. Sho-63-16313. An idler 3 is rotatably attached to one end in the longitudinal direction of the track frame 2, and the sprocket 4 is rotatably attached to the other end. To brackets fixed to the lower part of the track frame 2, a plurality of fixed track wheels 11 are rotatably attached at predetermined intervals. The crawler 6 is wound around the idler 3, sprocket 4, and track wheels 11, and the track wheels 11 rolls on the tread of the crawler 6. If a foreign matter such as a rock enters between the track wheel 11 and the crawler 6, the track wheel 11 comes off from the crawler 6 or meanders. Consequently, to prevent a foreign matter from entering the space between the track wheel 11 and the crawler 6, a fixed cover 51 covering the outer side face of the plurality of track wheels 11 is integrally attached so as to extend from the idler 3 to the sprocket 4 in the lower part of the track frame 2.
On the other hand, a crawler travel device in which a crawler is prevented from coming off by preventing a track wheel from running on the tread of the crawler by making the track wheel follow a change in the vertical direction of the crawler due to rough or uneven terrain at the time of travel, and which realizes stable high-speed driving is also known. FIG. 8 shows a second prior art of the crawler travel device and is a side view of, for example, a travel device having a swingable track wheel disclosed in Japanese Unexamined Patent Application No. Sho-53-53843.
In FIG. 8, at both ends in the longitudinal direction of the track frame 2, idlers 3 and 3 are rotatably attached to one end on the outside of first arms 53 and 53 provided so as to swing vertically, an almost center part of each of second arms 55 and 55 is swingably attached to one end on the inside of each of the first arms 53 and 53, and a pair of front and rear swingable track wheels 11 and 11 are rotatably attached to both front and rear ends of each of the second arms 55 and 55 which are swingable in the vertical direction. In the lower part of the track frame 2 between the front and rear idlers 3 and 3, an almost center part of the second arm 55 is swingably attached to the tip of a third arm 56 provided so as to be vertically swingable, and the pair of front and rear swingable track wheels 11 and 11 are rotatably attached to both front and rear ends of the second arm 55. Further, above the track frame 2, the sprocket 4 is rotatably attached in the rear part of the body. A crawler 6 is wound around the idlers 3 and 3, sprocket 4, and plurality of swingable track wheels 11. An elongated guide member 54 is attached to the lower end of each of the first arms 53 by a bolt. The guide members 54 are positioned on both sides of the crawler width direction so as to be in contact with the outer side faces of a link (not shown) of the crawler 6. Further, an elongated member 57 is attached to the lower end of the third arm 56 by a bolt, positioned along both sides in the crawler width direction, and also positioned so as to be in contact with the link of the crawler 6.
The elongated guide member 54 and elongated member 57 position in the transverse direction of the crawler 6 with respect to the track frame 2 and the track wheels 11 and 11, thereby preventing the crawler from coming off.
In recent years, to prevent the crawler from coming off when a crawler work vehicle such as bulldozer or hydraulic excavator travels on an uneven ground and to assure stability of high-speed travel, a travel gear having a swingable (so-called bogie type) track wheel is often used. Therefore, in the travel gear having the swingable track wheel as well, it is very important to prevent a foreign matter from entering the space between the track wheel and the crawler.
However, in the conventional travel gear having the swingable track wheel 11 described in Japanese Unexamined Patent Application No. Sho-53-53843, although the crawler is prevented from coming off at the time of driving on uneven ground by the guide member 54 and elongated member 57 attached to the lower ends of the arms 53 and 56 which swing vertically so as to follow vertical movement of the crawler 6, since no guard member is provided, intrusion of a foreign matter into the space between the track wheel 11 and the crawler 6 cannot be prevented. Consequently, there is a problem that wear of the crawler link and the track wheel 11 is severe due to the intrusion and the durability is not satisfactory. Since the two swingable track wheels 11 and 11 at both front and rear ends of the track frame 2 and the idler 3 are attached to both ends of the first arm 53, by influence of the vertical movement of the idler 3, the upper and lower positions of the swingable track wheels 11 and 11 at the both rear and front ends and the guide member 54 are determined. It is difficult to prevent coming-off of the crawler at both front and rear ends and intrusion of a foreign matter with reliability.
On the other hand, even if the fixed cover 51 integrally attached to the track frame 2 as used for the travel gear according to the first prior art disclosed in Japanese Patent Publication No. Sho-63-16313 is applied to the travel gear having the swingable track wheel, there is a problem such that when the track wheel 11 is lowered by the swingable arms 53 and 56, the cover 51 cannot sufficiently prevent intrusion of a foreign matter.
As described above, also in the travel gear having track wheels which can swing vertically, development of a travel gear capable of preventing intrusion of a foreign matter into a space between the track wheel and the crawler is strongly demanded.
The invention has been achieved by paying attention to the problems and its object is to provide a travel gear of a crawler work vehicle capable of preventing intrusion of a foreign matter into a space between a swingable track wheel and a crawler.
To achieve the object, according to the invention, there is provided a travel gear of a crawler work vehicle, in which a pair of right and left track frames are provided in the longitudinal direction in the lower part of the vehicle and a plurality of double bogie type track wheel devices are attached in the lower portion of the track frames, each double bogie type track wheel device including: a first arm member attached to the lower part of the track frame so as to be swingable in the vertical direction; a second arm member of which almost center portion in the longitudinal direction is rotatably attached to a tip of the first arm member so that both front and rear ends of the second arm member are swingable in the vertical direction; and a pair of front and rear track wheels rotatably attached to the front and rear ends of the second arm member and rotating on a tread of a crawler rotatably wound around the track frames, wherein a pair of first guard devices for preventing intrusion of a foreign matter into a space between the pair of front and rear track wheels and the crawler are attached to both side faces in the width direction of the vehicle of the first arm member.
According to the invention, the guard device is attached to each of the right and left side faces (inside and outside of the vehicle body) of the first arm member of each double bogie type track wheel device and intrusion of a foreign matter into a space between the pair of track wheels attached to the front and rear ends of the second arm member and the crawler is prevented by the guard device. Consequently, even when the track wheels move vertically in association with swing of the first and second arm members, intrusion of a foreign matter is prevented with reliability. Therefore, wear of the crawler link of the travel gear having bogie type track wheels and the track wheels is prevented, so that durability can be improved, and the crawler can be prevented from coming off.
In the invention, the first guard devices may have a size covering almost the whole swing range of at least the outside diameters of the pair of front and rear track wheels in association with vertical swing of the second arm member in cross section.
With the configuration, since the guard devices attached to the first arm member have the size covering almost the whole swing range of at least the outside diameters of the pair of front and rear track wheels in cross section even when the second arm member moves vertically, intrusion of a foreign matter can be prevented with reliability irrespective of vertical movement of the track wheels.
Further, in the invention, the first guard device may be formed almost in a plate shape, a lower end in cross section of the first guard device may be positioned at the level of almost the center of a link pin of the crawler on plain land, and a crawler link guide for guiding the link of the crawler may be attached to the lower part of the first guard device.
With the configuration, since the first guard device is formed almost in a plate shape, it can be manufactured with a simple structure at low cost. Since the lower end of the guard device is positioned at the level of almost the center of the link pin of the crawler on plain land, even when the track wheels swing downward, a foreign matter does not easily enter the space between the crawler and the track wheel, so that intrusion of a foreign matter can be prevented with a simple structure. Further, the crawler link is guided by the crawler link guide attached to the lower part, so that the crawler can be prevented from coming off with reliability.
According to another invention, a pair of right and left second guide devices are attached to a lower end portion of the track frame between neighboring two track wheels attached to different second arm members of two double bogie type track wheel devices.
According to the invention, by covering the gap between the two neighboring track wheels attached to different second arm members of two double bogie type track wheel devices with the second guide devices, intrusion of a foreign matter from the gap is prevented. Therefore, by using both the first guard device swingable corresponding to the bogie type track wheel and the fixed-type second guard device, an effect at preventing intrusion of a foreign matter is obtained in the whole area of the track frame.
In the invention, the second guide devices may have areas overlapped with the first guide devices of neighboring double bogie type track wheel devices at least at front and rear ends in cross section on plain land.
With the configuration, since at least the front and rear ends of the first and second guide devices are overlapped in cross section on plain land, even if the first guide device moves vertically, no gap is created between the devices, so that intrusion of a foreign matter can be prevented with reliability in the whole area of the track frame. In the overlapped area, by deviating the first and second guide devices to the outside and inside of the crawler, interference can be eliminated.
In any of the inventions, an idler and a sprocket may be attached on an almost extension line in the longitudinal direction of the track frame so that their attachment positions in the vertical direction are fixed.
With the configuration, the idler and the sprocket are attached linearly on an almost extension line in the longitudinal direction of the track frame. Moreover, by applying the invention to a travel gear in which the attachment positions in the vertical direction are fixed, to be specific, a travel gear which does not have the configuration that the track wheel and the idler are attached swingable in the vertical direction by an arm as described in the prior art, a higher effect is obtained. That is, without being influenced by the vertical swing of the idler, the track wheels always move vertically so as to follow a change in the vertical direction of the crawler, and moreover, even when the track wheel moves vertically, the swingable guard device follows the vertical movement and guards the track wheel. Therefore, also in the travel gear of a crawler work vehicle having bogie type track wheels, intrusion of a foreign matter into the space between the crawler and the track wheels can be prevented.